@Chugi
You really should go to a doctor to be checked for the pain.
If you are out of breath, trouble breathing, or more pain, after exercise or exertion, or the pain starts while you are doing something, then could be heart-related. Or lungs.
If pain is worse with empty stomach, then could be ulcers.
Too many possibles, we cannot guess.
I hope you will see a doctor and find out.
Might just be muscles or me/cfs pain, but we cannot tell you if it is serious or not, and we don't know if it is easily treatable , like stomach ulcers hurt a lot and are treatable .